Dr Michelle Dickinson: nanotechnologist on the new research examining space debris

The Sunday Session with Francesca Rudkin

Remember chlorofluorocarbons (CFCs)? These gases were once widely used as refrigerants in products like refrigerators and air conditioners, and to propel substances like hairspray out of aerosol cans.

Recently, CFCs have resurfaced in the news due to a new study examining space debris.

CFCs are notorious for damaging the ozone layer, a crucial shield that protects Earth from harmful ultraviolet radiation. Thanks to the 1987 Montreal Protocol, which regulates the use of these gases, the ozone hole above Antarctica is expected to heal within 50 years.

However, new research published in the journal Geophysical Research Letters introduces a fresh challenge. This study reveals that old satellites, when re-entering Earth's atmosphere and disintegrating, release aluminium oxide nanoparticles.

These nanoparticles react with residual atmospheric chlorine from CFCs, further depleting the ozone layer. Alarmingly, aluminum oxides, which are not consumed in this reaction, continue to destroy ozone molecules for decades as they descend through the stratosphere.

Currently, there are about 8,100 objects in low Earth orbit, 6,000 of which are Starlink satellites providing global internet access. Starlink plans to launch an additional 42,000 satellites, 12,000 of which have already been approved, and other companies, including Amazon, are also planning to deploy thousands of their own satellites.

These low Earth orbit internet satellites have a lifespan of approximately five years, after which they are left as space junk, eventually burning up in our atmosphere. The study found that between 2016 and 2022, the presence of these nanoparticles increased eightfold—a trend that will continue as more satellites are launched.

Researchers calculated that one satellite will produce about 30 kilograms of aluminium oxide nanoparticles during its atmospheric re-entry, and these particles can take up to 30 years to reach stratospheric altitudes, where 90% of Earth's ozone resides.

They estimated that once all planned satellite constellations are operational, around 912 metric tons of aluminium will be released annually, resulting in approximately 360 metric tons of aluminium oxides entering the atmosphere each year.

This represents a 646% increase over natural levels, posing a significant threat to the future of our ozone layer, which is essential for protecting life on Earth from harmful ultraviolet radiation.

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